The correct option is A Dirt
If we observed 2nd and 3rd letter of all 5 words we found that
In Dirt - 2nd letter i , 3 rd latter r
In Discount 2nd letter i, 3rd latter s
In Dozen 2nd lette o, 3rd letter z
In Drug 2nd letter r and 3rd latter u
In Dummy 2nd letter u and 3 rd Letter m
So if we are arranged in alphabetical order as in a Dictionary
Then,
Dirt > Discount > Dozen > Drug > Dummy will come.